1. Field of the Invention
The present invention generally relates to computer user interfaces presented on a display screen and, more particularly, to a graphic user interface (GUI) which easily accomplishes both a scale change function with a panning or scrolling function.
2. Description of the Prior Art
In many computer application programs, and in particular graphics programs such as computer aided design and drafting (CAD) programs, the drawing is much larger than the physical display. The physical display shows the "working area" of the drawing which is some subset of the entire drawing or map, sometimes referred to as the "virtual screen". That is, the physical screen size, which is determined by the physical dimensions of the display device connected to the computer system, typically displays only a portion of the total drawing or map. This portion of the total drawing or map, or the "working area", is the current area of interest for viewing, drawing or editing. CAD programs therefore implement a scrolling function, called panning, to allow the user to move about in the virtual screen thereby changing the working area, and a scaling function, called zooming, to allow the user to view either a larger or smaller portion of the working area, depending on the level of detail that the user wishes to see.
Any sort of drawing or viewing program requires a means of moving around, by scrolling or panning, a virtual screen which may be larger than the physical screen area, as well as a means of changing scale (to zoom in or zoom out). For panning control, the use of scroll bars is well established, but there is no method in common use for changing the display scale. There are, in fact, a multitude of ways to change the display scale; however, all require extra steps by the user and/or take up screen space that could be better used for the task at hand. For example, there are many methods in use for changing the display's scale that involve bringing up additional controls or interfaces on the screen. These include, but are not limited to, prompted entry fields, sliders, spin buttons, single-selection (radio) buttons, multiplier buttons (e.g., 2.times., 1/2.times. scale), etc. found within pull-down menus, pop-up dialogues, fixed screen areas, etc. All of these methods have one thing in common, and that is they take up space on the display that could better be used for an end task, such as a CAD drawing or a map. Additionally, some require one or more extra operations to invoke them (e.g., select Menu Bar options, then select Scale Change from the pull-down menu's list).